The screw compressor includes, for example, a pair of screw rotors of a male rotor and a female rotor which are engaged with each other. The male rotor and the female rotor are rotatably supported by roller bearings and ball bearings, respectively.
Each of the rolling bearing and the ball bearing has a rolling surface or a sliding surface. It is necessary to form thin oil films on these surfaces to prevent direct contact between metals, therefore, oil lubrication is required. As advantages of oil lubrication, discharge of frictional heat, extension of a bearing lifetime, prevention of rust, prevention of foreign matter intrusion and so on can be cited in addition to reduction of friction and abrasion.
As the screw rotor rotates at high speed, frictional heat is generated at respective bearing portions. Accordingly, a force fed lubrication system in which respective bearings are lubricated by forcibly feeding lubricating oil into the bearings and generated frictional heat is discharged to the outside through the forcibly fed lubricating oil in respective bearings is adopted.
That is, oil passages communicating with respective bearings are provided in a casing or the like of the screw compressor to perform the forced lubrication in which lubrication oil is forcibly fed to respective bearings through the oil passages by utilizing a differential pressure between a discharge-side pressure and a suction-side pressure of the screw compressor.
As this kind of related art, there are one described in JP-A-2014-118931 (Patent Literature 1) and so on.